Building performance references

daylighting performance | solar control performance | active façade performance | double-skin façade and natural ventilation performance

Daylighting performance

Monitored performance data of various innovative daylighting systems are given in the International Energy Agency Task 21 Daylight in Buildings publication: “Daylight in Buildings: A Source Book on Daylighting Systems and Components” in Chapter 4. See http://eetd.lbl.gov/Bookstore.html under Practical Guides & Tools for Energy Users for “Daylight in Buildings: A Source Book on Daylighting Systems and Components”. For those residing outside of the U.S. or Canada, please visit http://www.iea-shc.org.

Daylighting image banks were created using the Radiance visualization tool for “typical” window configurations. These can be viewed at:
http://gaia.lbl.gov/rid/ http://www.bwk.tue.nl/fago/daylight/varbook/index.html

Monitored daylighting data are given in the reference:
Fontoynont, M. and European Commission Directorate-General XII Science Research and Development (1999). Daylight performance of buildings. London, James & James (Science Publishers) for the European Commission Directorate General XII for Science Research and Development.

Solar control performance

Retrofit sail to address shading problem in Waterloo Train Station, London, Architect: Nicholas Grimshaw

The 2001 ASHRAE Handbook: Fundamentals, Chapter 30 describes the underlying building physics of fenestration systems. LBNL with ASHRAE developed a simplified method for determining the SHG of shaded windows, which is detailed in the new handbook. For mechanical system design, engineers are interested in modeling shaded windows. With the old handbook, engineers would use the solar coefficient tables which were dispensed with in the 2001 version. A simplified method was needed to allow users to make gross assumptions for their calculations without reliance on dated calorimeter measurements.
http://www.ashrae.org

International Energy Agency (IEA) Task 27: Performance of Solar Façade Components. The objectives of this research task are to determine the solar, visual, and thermal performance of materials and components, such as advanced glazings, and to promote increased confidence in the use of these products by developing and applying appropriate methods for the assessment of durability, reliability, and environmental impacts. The scope of the task includes dynamic glazings, such as electrochromics, daylighting products, solar protection devices such as venetian blinds, and double-envelope systems.
http://www.iea-shc.org/

The Lund Institute of Technology in Sweden is conducting a Solar Shading Project which will 1) measure solar energy transmittance, 2) develop advanced computer programs and a user-friendly design tool (ParaSol) to predict the impact of shading devices on the energy use in buildings, 3) conduct paramet-ric studies for the development of design guidelines, and 4) measure daylight conditions in rooms equipped with shading devices.
http://www.byggark.lth.se/shade/shade_home.html

Active façade performance

The École Polytechnique Fédérale de Lausanne (EPFL) is conducting two projects at the Laboratoire d’Energie Solaire et de Physique du Batiment called 1) Projet UE Smart Window: An Innovative, Adaptive, Independently-Controlled Window System with Smart Controlled Solar Shading and Ventilation and 2) Projet UE EDIFICIO: Efficient design incorporating fundamental improvements for control and integrated optimization. The projects involve the integration of intelligent systems using genetic algorithms and adaptive controls.
http://lesowww.epfl.ch

The National Research Council Canada, Institute for Research in Construction is conducting a three-year project on how office occupants actually use both manually- and automatically-controlled blinds and lighting systems. This will help establish realistic expectations about the possible benefits of daylighting in office buildings considering how occupants use blinds and other anti-glare devices.
http://www.nrc.ca/irc/  

or contact Christoph Reinhart at christoph.reinhart@nrc.ca

The Centre for Window and Cladding Technology at the University of Bath, UK conducted a study called Integrated Building Control (IBC) to develop a window with automated vents and shading. Self-adaptive control strategies were applied to the window in order to moderate the environment in the room but allow for the needs of the occupant.
http://www.cwct.co.uk/pubs/

A monitored field test of large-area electrochromic windows was conducted by LBNL. Further work to evaluate EC windows will commence in mid-2002. For published results, see:

Lee, E.S., D. L. DiBartolomeo. 2000. “Application issues for large-area electrochromic windows in commercial buildings.” Solar Energy Materials & Solar Cells 71 (2002) 465–491. LBNL Report 45841, Lawrence Berkeley National Laboratory, Berkeley, CA.
http://eetd.lbl.gov/BTP/pub/OMpub.html

Monitored lighting energy use and cooling load data, human factors data, and controls data from a full-scale field test were reported for an automated venetian blind and dimmable lighting system. For published results, see:

Lee, E.S., D. L. DiBartolomeo, E.L. Vine, S.E. Selkowitz. 1998. “Integrated Performance of an Automated Venetian Blind/Electric Lighting System in a Full-Scale Private Office.” Thermal Performance of the Exterior Envelopes of Buildings VII: Conference Proceedings, Clearwater Beach, Florida, December 7- 11, 1998. LBNL Report 41443, Lawrence Berkeley National Laboratory, Berkeley, CA.

Vine, E., E.S. Lee, R. Clear, D. DiBartolomeo, S. Selkowitz. 1998. “Office Worker Response to an Automated Venetian Blind and Electric Lighting System: A Pilot Study.” Energy and Buildings 28(2)1998:205-218. LBNL Report 40134, Lawrence Berkeley National Laboratory, Berkeley, CA.
http://eetd.lbl.gov/BTP/pub/ISpub.html

Double-skin façades and natural ventilation performance

COST C13 Action on Glass and Interactive Building Envelopes

The European Co-operation in the field of Scientific and Technical Research (COST) C13 Action on Glass and Interactive Building Envelopes involves the collaboration of approximately 30 scientists from 12 EU countries. The C13 action is a networking activity where scientists from the EU community are engaged to define the state-of-the-art R&D in the area of interactive façades, to collaborate on common research activities, to identify areas of future required research, and to disseminate results of the activity to the architectural and engineering community. Three scientific programmes or working groups (WG) have been defined for the COST Action C13: 1) architectural aspects, 2) quality of interior space, and 3) structural concepts. The programme is voluntary (no R&D funds) and slated to occur over a 3-year schedule (initiated around June 2000).
http://erg.ucd.ie/costc13/index.html

See reference to IEA Task 27 above.

The Chartered Institution of Building Services Engineers (CIBSE) publishes Applications Manuals: AM10, AM11 and AM13 on natural ventilation modeling.
http://www.cibse.org/

There is an international collaboration on research for natural ventilation and hybrid ventilation:
http://hybvent.civil.auc.dk

The Glass Construction Manual explains some of the fundamentals of double-skin façades as well as other advanced façade systems: Schittich, C., G. Staib, D. Balkow, M. Schuler, and W. Sobek. 1999. Glass Construction Manual. Munich: Birkhauser Publishers for Architecture.

The VTT Building Technology Group in Espoo, Finland is conducting a study on the development of tools for characterizing and planning double-skin façades. Results are as yet unpublished.
http://www.vtt.fi/rte/projects/

Helsinki University of Technology recently published a field study documenting post-occupancy conditions and the design/ construction process by Sini Uuttu called the Current Structures in Double-Skin Façades. The study can be accessed through the library at the portal:
http://www.glassfiles.com

Natural ventilation and night-time cooling strategies were designed for the new San Francisco Federal Building. See:

McConahey, E., P. Haves, and T. Christ. 2002. “The Integration of Engineering and Architecture: A Perspective on Natural Ventilation for the New San Francisco Federal Building.” To be presented at the ACEEE 2002 Summer Study on Energy Efficiency in Buildings: Energy Efficiency in a Competitive Environment, August 18-23, 2002, Asilomar, Pacific Grove, CA and published in the Proceedings. Washington, D.C.: American Council for an Energy-Efficient Economy.

Some monitored data are given in the reference:
Oesterle, Lieb, Lutz, Heusler. 2001. Double-Skin Façades: Integrated planning. Munich: Prestal Verlag.

Multi-layer skin façade, debis Headquarters, Berlin

"A Critical Review of Double-Skin Façades"

There are very few articles that provide a critical review of double-skin façades and the few that are available are in German. We reviewed a widely cited German article written by Dr. Karl Gertis, who is the director of the Fraunhofer Institute of Building Physics in Stuttgart, Germany and renown expert in the field, and paraphrase part of the article below. The article is entitled: "Sind neuere Fassadenentwicklungen bauphysikalisch sinnvoll? Teil 2: Glas-Doppelfassaden (GDF)" published by ©Ernst & Sohn Bauphysik 21 (1999), Heft. 

Gertis summarizes his findings as follows: Innovative façades have recently been developed - or rather have become fashionable. Glass double façades (GDFs) are at present being discussed in a very rigorous and controversial way. Some consider them an expression of modern design and a forward-looking, ecological façade concept with a promising future. Others consider them skeptically, i.e., as mistaken in our local (German) climate. In this paper, the different types of GDFs are explained systematically. The extensive GDF literature is evaluated critically. Building physics investigation results are presented. This results in an overall GDF synopsis in performance of acoustics, airflow, thermal, energy use, daylight as well as moisture and fire protection. Conclusion: Simulations cannot be relied on and practical measurement results are lacking. There is a lot of work to catch up on. It becomes apparent that GDFs - apart from special cases - are unsuitable for our local climate from the building physic's point of view. Moreover, they are much too expensive. If they are nevertheless designed in order to keep up with architectural fashion, building physics support is indispensable. 

The paper then introduces the current situation. In Germany, GDFs are increasingly being introduced in high-rise buildings where there are few architectural competitions where a GDF is not presented with impressive terminology that belie any real results. Contractors and building owners also use this impressive terminology in cited literature. Putting aside these claims, one must question whether such promises are realized. One early scientific study with measured results showed that the Building of Economic Advances in Duisburg with a GDF façade has an annual total energy consumption of 433 kWh/m² (40 kWh/ft²-yr) and should thus be qualified as an energy guzzler, who's energy consumption even surpasses some of the older buildings. The Commerze Bank in Frankfurt, which also has a GDF façade, has an annual total energy consumption of 169 kWh/m², (15.6 kWh/ft²-yr) which will most likely prove to be too low. 

After characterizing the different types of GDF systems, the author then goes on to explain what the current level of knowledge is on façade performance. In the early 1990s, much of the literature was extremely positive with no quantitative proof given for performance claims. The focus of the literature was how GDFs set new levels for energy use and quality of the work environment (the author notes that they are new levels in the negative sense!). A significant amount of non-critical literature has been published by architectural magazines. For many articles, the claimed performance has proven later to be wrong or untrue. From 1996 onwards, more critical reviews have been published indicating increased dissatisfaction with GDFs and countering the euphoric descriptions from the early 1990s. The author cites some problems noted in the literature. For example, window insect screens cannot be used with natural ventilation because the airflow is to weak to overcome the pressure loss over the air filter. During significant portions of the year, one cannot achieve a comfortable indoor climate with natural ventilation through GDFs, and GDF buildings without active cooling fail. Arriving at a design solution for a GDF is possible but is much too expensive. And GDFs cannot be used as a substitution for room air-handling measures. The author also notes several problems with literature that cite simulation results. First, the results are usually given for hypothetical boundary conditions with a simulation model developed early in the design process. Often the boundary conditions are not exactly stated so the results are fairly useless since no critical interpretation can be made. Other sources provide measurements made under laboratory conditions. Very few publications have real world measurements. The GDF building in Wurvdurg, which was built with many technical innovations such as radiant cooling, has an annual total energy use of 58.9 kWh/m²-yr (5.4 kWh/ft²-yr). 

The author cites costs from various publications, noting that the investment costs are very high compared to conventional punched hole façades with high-efficiency windows. Costs such as $680/m² and up are mentioned. In another reference, the added cost for a GDF is estimated at 70%. Another source mentions $135-360/ m², while the costs for the GDF at Dusseldorf Stadttor (see Detailed Case Studies section) was given at $585/m². 

A summary table is then given by the author which is paraphrased in this report. He notes that the "con" arguments are often more important than the "pro" arguments and that more measurements under real-world circumstances are needed to clarify the real performance of these systems.

Detailed analysis of various performance parameters are then made by the author. With acoustics, several key points were made. For a given example, the potential sound reduction by a second exterior skin is compromised if the openings for ventilation exceed about 16% of the façade. The level of sound reduction achieved with a GDF can also be achieved with other measures. Partitioning the sound by dividing the GDF air cavity into smaller compartments can reduce sound transmittance to adjacent rooms; however, doing so can compromise other performance aspects of the façade (e.g., airflow, daylighting, etc.). With reduced exterior noise levels, the subjective perception of noise from adjacent rooms is increased. There are many GDF cases where interior dividing walls have to be retrofit with increased sound insulation. 

With respect to airflow in the gap and air exchange within the room, the author critiques the assumptions behind several literature references. The references and other simulations assume that airflow in the gap will be upwards based on thermal driven flow and downwards based on wind load on the building (the higher wind load will give a higher static pressure). Actual airflow patterns in the gap will differ; there is instationary airflow exchange on the leeward and windward sides of the building and within the air gap. Instationary fluctuations in air pressure can be very strong. Also, airspeed in the gap gets smaller with increased exterior wind speed, due to the air resistance within the façade. 

For Venetian blinds positioned in the air gap, the devices should be and remain reflective (in the wavelength that the exterior glass is transmitting) to prevent temperature increase in the air gap. This poses additional costs, since continuous cleaning of blinds is known to be complicated and involved. 

The air temperature in the gap can create significant thermal discomfort and force closure of interior windows designed to allow natural ventilation. The author gives an example where the temperature of a southwest-facing GDF is given as a function of air changes in the gap and the total solar transmittance of the exterior skin with shading devices. For an exterior air temperature of 30°C, the air temperature of the gap can approach 40-50°C. Substantial cooling is not achieved until the air change rate within the cavity is 20, which is hard to achieve with natural ventilation and reasonable air gaps, unless the façade is opened to more than 30%, which then eliminates the acoustical performance of the façade. In order to achieve low air temperatures in the gap, one could also reduce the total solar energy transmittance to a maximum of 0.30, but the interior room will get very dark and increase electric lighting energy use. 

The author notes that GDF buildings usually have high internal loads, so dealing with high internal loads in the summer is more important than heating during the winter. An example is given of interior temperatures over time with different types of ventilation (mechanical with and without night-time ventilation versus GDF natural ventilation) and different levels of expected air changes per hour during the day and night. With natural ventilation through the GDF, the maximum interior temperature is 46°C. The author concludes that the GDF and natural ventilation is almost a contradiction in terms (citing other research that confirms this from 1996-1997). 

The article continues to discuss daylighting, moisture and condensation, and fire performance, however these portions of the article were not translated.

Question/Information: eslee@lbl.gov